/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System;

namespace Lucene.Net.Search.Spans
{
	
	/// <summary>Expert: an enumeration of span matches.  Used to implement span searching.
	/// Each span represents a range of term positions within a document.  Matches
	/// are enumerated in order, by increasing document number, within that by
	/// increasing start position and finally by increasing end position. 
	/// </summary>
	public abstract class Spans
	{
		/// <summary>Move to the next match, returning true iff any such exists. </summary>
		public abstract bool Next();
		
		/// <summary>Skips to the first match beyond the current, whose document number is
		/// greater than or equal to <i>target</i>. <p/>Returns true iff there is such
		/// a match.  <p/>Behaves as if written: <pre>
		/// boolean skipTo(int target) {
		/// do {
		/// if (!next())
		/// return false;
		/// } while (target > doc());
		/// return true;
		/// }
		/// </pre>
		/// Most implementations are considerably more efficient than that.
		/// </summary>
		public abstract bool SkipTo(int target);
		
		/// <summary>Returns the document number of the current match.  Initially invalid. </summary>
		public abstract int Doc();
		
		/// <summary>Returns the start position of the current match.  Initially invalid. </summary>
		public abstract int Start();
		
		/// <summary>Returns the end position of the current match.  Initially invalid. </summary>
		public abstract int End();
		
		/// <summary> Returns the payload data for the current span.
		/// This is invalid until {@link #Next()} is called for
		/// the first time.
		/// This method must not be called more than once after each call
		/// of {@link #Next()}. However, most payloads are loaded lazily,
		/// so if the payload data for the current position is not needed,
		/// this method may not be called at all for performance reasons. An ordered
		/// SpanQuery does not lazy load, so if you have payloads in your index and
		/// you do not want ordered SpanNearQuerys to collect payloads, you can
		/// disable collection with a constructor option.<br/>
		/// 
		/// Note that the return type is a collection, thus the ordering should not be relied upon.
		/// <br/>
		/// <p/><font color="#FF0000">
		/// WARNING: The status of the <b>Payloads</b> feature is experimental.
		/// The APIs introduced here might change in the future and will not be
		/// supported anymore in such a case.</font><p/>
		/// 
		/// </summary>
		/// <returns> a List of byte arrays containing the data of this payload, otherwise null if isPayloadAvailable is false
		/// </returns>
		/// <throws>  java.io.IOException </throws>
		// TODO: Remove warning after API has been finalized
		public abstract System.Collections.Generic.ICollection<byte[]> GetPayload();
		
		/// <summary> Checks if a payload can be loaded at this position.
		/// <p/>
		/// Payloads can only be loaded once per call to
		/// {@link #Next()}.
		/// 
		/// </summary>
		/// <returns> true if there is a payload available at this position that can be loaded
		/// </returns>
		public abstract bool IsPayloadAvailable();
	}
}